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# Air - Prandtl Number

## Prandtl number for air vs. temperature and pressure.

The Prandtl Number - Pr - is a dimensionless number approximating the ratio of momentum diffusivity (kinematic viscosity) to thermal diffusivity - and is often used in heat transfer and free and forced convection calculations.

The Prandtl number can for calculations be expressed as

Pr =  μ cp / k                           (1)

where
μ = absolute or dynamic viscosity [kg/(m s)], [lbm /(ft h)]
cp = specific heat [J/(kg K)], [Btu/(lbm oF)]
k = thermal conductivity [W/(m K)], [Btu/(h ft2oF/ft)]

Below, Prandtl numbers for air at varying temperatures and pressures are given in figures and tables .

See also other properties of Air at varying temperature and pressure: Density and specific weight at varying temperature , Density at varying pressure , Diffusion Coefficients for Gases in Air , Specific heat at varying temperature and Specific heat at varying pressure , Thermal Conductivity , Thermal Diffusivity , Properties at gas-liquid equilibrium conditions and Air thermophysical properties at standard conditions and Composition and molecular weight ,
as well as Prandtl number of Ammonia , Carbon dioxide , Methane , Nitrogen , Propane and Water .

Air Prandtl number at 1 bara pressure, temperature given as °C or °F:

Air Prandtl number at varying temperatures and constant pressures, SI and Imperial units:

Air Prandtl number at 1 bara pressure, temperature given as °C or °F:

Air - Prandtl Number at 1 bara Pressure
Temperature Pr Temperature Pr
[°C] [-] [°F] [-]
-100 0.734 -150 0.733
-50 0.720 -50 0.719
0 0.711 0 0.714
25 0.707 60 0.709
50 0.705 75 0.708
100 0.701 100 0.706
150 0.699 200 0.701
200 0.698 300 0.699
250 0.699 400 0.698
300 0.702 500 0.700

Air Prandtl number at given temperatures and 1, 5 10 and 20 bara pressure:

Air - Prandtl Number
Temperature Prandtl number at given pressures
[K] [°C] [°F] 1 bara,
14.5 psia
5 bara,
72.5 psia
10 bara,
145 psia
20 bara,
725 psia
60 -213.2 -351.7 4.138 4.153 4.170 4.187
80 -193.2 -315.7 1.7 2.252 2.259 2.269
100 -173.2 -279.7 0.780 0.898 1.783 1.770
120 -153.2 -243.7 0.759 0.806 0.890 1.360
140 -133.2 -207.7 0.747 0.773 0.812 0.923
180 -93.2 -135.7 0.731 0.743 0.759 0.792
200 -73.2 -99.7 0.726 0.735 0.745 0.769
220 -53.2 -63.7 0.721 0.728 0.736 0.754
240 -33.2 -27.7 0.717 0.722 0.729 0.742
260 -13.2 8.3 0.713 0.718 0.723 0.734
273 0.0 32.0 0.711 0.715 0.720 0.729
280 6.9 44.3 0.710 0.714 0.718 0.727
289 15.6 60.0 0.709 0.713 0.716 0.723
300 26.9 80.3 0.707 0.711 0.714 0.722
320 46.9 116.3 0.705 0.708 0.711 0.717
340 66.9 152.3 0.703 0.705 0.708 0.714
360 86.9 188.3 0.701 0.703 0.706 0.711
380 106.9 224.3 0.700 0.702 0.704 0.709
400 126.9 260.3 0.699 0.701 0.703 0.706
500 226.9 440.3 0.698 0.700 0.701 0.703
600 326.9 620.3 0.703 0.704 0.704 0.706
700 426.9 800.3 0.710 0.710 0.711 0.712
800 526.9 980.3 0.717 0.718 0.718 0.719
900 626.9 1160.3 0.724 0.725 0.725 0.725
1000 726.9 1340.3 0.730 0.730 0.730 0.731
1100 826.9 1520.3 0.734 0.735
1500 1226.9 2240.3 0.743 0.743
1900 1626.9 2960.3 0.742 0.742

## Related Topics

• ### Air Psychrometrics

Moist and humid air calculations. Psychrometric charts and Mollier diagrams. Air-condition systems temperatures, absolute and relative humidities and moisture content in air.
• ### Fluid Mechanics

The study of fluids - liquids and gases. Involving velocity, pressure, density and temperature as functions of space and time.
• ### Gases and Compressed Air

Properties of air, LNG, LPG and other common gases. Pipeline capacities and sizing of relief valves.
• ### Material Properties

Properties of gases, fluids and solids. Densities, specific heats, viscosities and more.

## Related Documents

• ### Air - Composition and Molecular Weight

Dry air is a mechanical mixture of nitrogen, oxygen, argon and several other gases in minor amounts.
• ### Air - Density vs. Pressure and Temperature

Air density at pressure ranging 1 to 10 000 bara (14.5 - 145000 psi) and constant selected temperatures.
• ### Air - Density, Specific Weight and Thermal Expansion Coefficient vs. Temperature and Pressure

Online calculator, figures and tables showing density, specific weight and thermal expansion coefficients of air at temperatures ranging -100 to 1600 °C (-140 to 2900 °F) at atmospheric and higher pressure - Imperial and SI Units.
• ### Air - Diffusion Coefficients of Gases in Excess of Air

Diffusion coefficients (D12) for gases in large excess of air at temperatures ranging 0 - 400 °C.
• ### Air - Dynamic and Kinematic Viscosity

Online calculator, figures and tables with dynamic (absolute) and kinematic viscosity for air at temperatures ranging -100 to 1600°C (-150 to 2900°F) and at pressures ranging 1 to 10 000 bara (14.5 - 145000 psia) - SI and Imperial Units.
• ### Air - Humidity Ratio

The mass of water vapor present in moist air - to the mass of dry air.
• ### Air - Moisture Holding Capacity vs. Temperature

The moisture holding capacity of air increases with temperature.
• ### Air - Molecular Weight and Composition

Dry air is a mixture of gases where the average molecular weight (or molar mass) can be calculated by adding the weight of each component.
• ### Air - Properties at Gas-Liquid Equilibrium Conditions

Properties of air change along the boiling and condensation curves (temperature and pressure between triple point and critical point conditions). An air phase diagram included.
• ### Air - Specific Heat vs. Pressure at Constant Temperature

Figures and tables with isobaric (Cp) and isochoric (Cv) specific heat of air at constant temperature and pressure ranging 0.01 to 10000 bara.
• ### Air - Specific Heat vs. Temperature at Constant Pressure

Online calculator with figures and tables showing specific heat (Cp and Cv) of dry air vs. temperature and pressure. SI and imperial units.
• ### Air - Speed of Sound vs. Temperature

Speed of sound in air at standard atmospheric pressure with temperatures ranging -40 to 1000 °C (-40 to 1500 °F) - Imperial and SI Units.
• ### Air - Thermal Conductivity vs. Temperature and Pressure

Online calculator with figures and tables showing air thermal conductivity vs. temperature and pressure. SI and imperial units.
• ### Air - Thermal Diffusivity vs. Temperature and Pressure

Figures and tables withdry air thermal diffusivity vs. temperarure and pressure. SI and Imperial units.
• ### Air - Thermophysical Properties

Thermal properties of air at different temperatures - density, viscosity, critical temperature and pressure, triple point, enthalpi and entropi, thermal conductivity and diffusivity and more.
• ### Air Conditioning - Cooling of Air and Condensate Generated

Water may condensate when air is cooled in air conditioning systems.
• ### Air Properties - SI Units

Ideal gas properties of air at low pressure - SI units.
• ### Ammonia - Prandtl Number vs. Temperature and Pressure

Figures and table with changes in Prandtl number for ammonia with changes in temperature and pressure.
• ### Compressed Air - Pressure Drop Diagrams, Metric Units

Pressure loss in compressed air pipe lines.
• ### Methane - Prandtl number vs. Temperature

Figures and table showing changes in Prandtl number for methane with changes in temperature and pressure.
• ### Moist Air - Properties

Psychrometric table with humid air properties like saturation pressure, specific volume, enthalpy and entropy.
• ### Moist Air - Specific Volume

Specific volume of moist air is defined as the total volume of humid air per mass unit of dry air
• ### Moist Air - Weight of Water Vapor

Weight of water vapor in air
• ### Nitrogen - Prandtl number vs. Temperature and Pressure

Figures and tables showing Prandtl number of nitrogen at varying temperarure and pressure, SI and Imperial units.
• ### PP - PolyPropylene Pipes - Support Spacing

Maximum distance between PolyPropylene pipes supports.
• ### Propane - Prandtl Number vs. Temperature and Pressure

Figures and tables with Prandtl Number of liquid and gaseous propane at varying temperarure and pressure, SI and Imperial units.
• ### Propane - Thermal Diffusivity vs. Temperature and Pressure

Figures and tables showing thermal diffusivity of liquid and gaseous propane at varying temperarure and pressure, SI and Imperial units.
• ### Solubility of Air in Water

The amount of air that can be dissolved in water decreases with temperature and increases with pressure.

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## Citation

• The Engineering ToolBox (2018). Air - Prandtl Number. [online] Available at: https://www.engineeringtoolbox.com/air-prandtl-number-viscosity-heat-capacity-thermal-conductivity-d_2009.html [Accessed Day Month Year].

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